Can a change in portion size transform our bad food habits?

Research shows that people do not change their consumption patterns even with knowledge of how many calories they are consuming Photograph: PR

It is a commonly held view that calorific information on restaurant menus helps customers manage calorie consumption. In an online survey of visitors to the Sustainable Restaurant Association's website, over 60 per cent of respondents from the UK agreed. And in the halls of New York City's Board of Health they felt so strongly about the display of calorific values, it's been a legal requirement for short-order restaurants since 2008.

Firstly, it's not very informative – how many calories are you supposed to eat? How many have you eaten? What happens if you go over or under? It's unclear. And even if you've got that nailed, it requires a heavy cognitive load to work it out. Secondly, the signs have a terrific provincial problem – you've already decided you want to eat, have selected an outlet, and are at the point of choice before you're exposed to the calorie-count. Are you inclined to change your choice or leave at this stage? It's unlikely – you're pretty committed by then.

Can we create a menu that helps customers manage calorie consumption?

Plates size is an easy win and familiar to weight-loss folk. The eye considers the meal more voluminous when it fills a small plate compared to the same sized portion on a larger plate and this tricks us into 'feeling' more full. But this isn't practical for widespread adoption by short-order restaurants. We need to find something universal, persistent, and inexpensive.

It's a tough ask.

Dan Ariely, Professor at Duke University and author of The Upside of Irrationality, and Predictably Irrational, runs classes on behavioural economics in which the CEO of a Chinese restaurant business had enrolled. The CEO asked Dan how he could help his patrons make healthier choices in his restaurants. Dan and his team took one of the restaurants and experimented with the menu.

The obvious place to start was to offer two portion sizes – small and large. In practice, the idea bombed for main dishes so they tried it for side orders. When offered a full-rice/full-price and a half-rice/half-price option nearly 40 per cent of guests took the half-rice option. That's a significant proportion of diners who cut 250 calories from their meal.

As successful as that was, it left the restaurant owner with a problem: reduced profit. The rice dishes have a high mark-up, so half-rice/half-price is noticeably punishing. This situation could remain and therefore the CEO would need to run his restaurants in favour of his patrons but at the expense of his competitiveness. Is this acceptable?

There was one experiment left.

Using a rather counter-intuitive approach, the team kept the half-rice option on the menu, but priced it the same as the full-rice option. It worked. Simply by asking, "Would you be interested today [to] get half an order of rice?" 40 per cent of customers chose the half portion even though it was no cheaper.

This fixed the profit problem but how?

We tend to eat what is put in front of us and we find it very difficult to stick to long-term commitments when we're 'in the moment'. Put these two things together and those that want to control their calories have a problem. However, we are better at making and sticking to commitments made for the future. This is where the half-rice option comes into play – you can choose to remove temptation from your plate ahead of time. This is why price didn't affect the rice portion choice.

With this 'Odysseus and the Sirens' option they nailed a solution to calorie management that's universal, persistent, and inexpensive (to say the least).

Some claim – much like George Loewenstein and Peter Ubel writing in the New York Times – that because calorific information doesn't alter behaviour, the only other option is to add tax. A junk food tax would be effective, but to be universal and persistent it needs to be legislated and policed, otherwise behaviour would not change and its pernicious nature would erode social capital.

The behavioural sciences could help ameliorate the punitive nature of taxation, but I think it's better-employed streamlining menu choice architecture. Or at least to get that sorted out first. After all, even though we can't liberate ourselves from our behavioural quirks, we can work them in our favour. Or, in this case, in favour of those that want to manage their calories.

Half-rice anyone?

Oliver Payne is an advertising professional, the founder of behavioural communications agency The Hunting Dynasty, and author of Inspiring Sustainable Behaviour: 19 Ways To Ask For Change

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